1. Field of the Invention
This invention relates to processes of fabrication of elastomer or plastomer tubes, in particular surgical tubes, by extrusion of aqueous dispersions of particles made sensitive to heat.
2. Description of the Prior Art
Processes for the fabrication of elastomer and plastomer tubes by extrusion of obvious dispersions are known, one example being those processes developed by the English company Revertex Limited and known under the name of "Revultex processes." Unfortunately, these processes cannot be transformed into continuous extrusion processes, because the aqueous serum which is exuded from the wall of the tube during gelling, during shrinking of this gel, both on the outside face and inside face of this wall, can be eliminated by washing only by permitting the wash water easily to penetrate on the inside of the tube through the front end of this tube, and possibly through its back end after prior cutting of said tube at the exit of the extruder, i.e., after its passage in a chamber known as the "hot chamber" through which pass a tube and a central coaxial glass core, forming a shaping unit of said elastomer tube.
Further, the washing time of sections of tubing is generally very high, although excessive washing has a tendency to take away antioxidizing elements which are incorporated in the original material and which are necessary to obtain products free of defects. This washing period can vary from four hours for thin tubes to twenty-four hours, for example, in the case of tubes 3 mm thick.
Further, in the case of thin tubes, the Revultex process provides for the passage of the elastomer tube for about five minutes in a bath containing a weak solution of formic or acetic acid to increase the density and mechanical resistance of the gel making up the tube wall.
Finally, before final drying, the Revultex process provides for the passage of the elastomer tube for about six minutes in a chlorination bath with possible circulation of a chlorinating solution inside the elastomer tube.
To make such a process continuous, it has been proposed to take the extruded tube directly by a horizontal conveyor belt into a drying tunnel, without intermediate rinsing and chlorination treatments, by sending compressed cold air into the elastomer tube closed at its front end, by means of a glass tube replacing the shaping core, to prevent sagging of the tube by gravity during the horizontal travel intended to bring it to said drying tunnel.
However, in such a process, the aqueous serum exuded toward the inside of the tube, tends by gravity to condense in the lower part of this tube which is in contact with said conveyor belt, and consequently, at the same time of drying inside said tunnel, which is brought to a sufficient temperature to perfect cohesion and give the tube the desirable density and mechanical resistance, there is a heterogeneity in the physical structure of the tube at the site where the serum gathers, in relation to the rest of the tube wall.